Multi-stage taper fan-motor assembly

ABSTRACT

A motor-driven fan assembly includes a bracket which couples to a motor assembly and includes an outlet port. A shroud assembly defines a first chamber and a second chamber and includes an inlet port, the shroud assembly is received on the bracket. A bearing-supported shaft is driven by the motor assembly, and extends through the bracket and into the shroud assembly. A first fan is coupled to the shaft and positioned in the first chamber. A second fan is coupled to the shaft and positioned in the second chamber. The first and second fan include a plurality of curved blades positioned between a flat disc and a cap, the cap defining a non-linear cross section. Rotation of the fans by the shaft results in air flow through the fan assembly. Dust is generally prevented from settling on the fan blades during operation, thereby preventing non-uniform dust buildup or breakup which may cause excessive vibration and reduce bearing and brush life.

TECHNICAL FIELD

The present invention is generally directed to motor assemblies. In particular, the present invention is directed to the fan portion of a motor assembly which increases motor efficiency and air flow characteristics. Specifically, the present invention is related to a multi-stage fan assembly with working air fans having nonlinear tapers which promotes efficiency and resists contaminant buildup.

BACKGROUND ART

Vacuum motors employing multi-stage tapered fans are used in many applications such as vacuum manipulators, packaging equipment, bag filling, cutting tables, appliances and exhaust air removal, to name just a few. Such vacuums designs generally include a cylindrical housing, or shroud, which encloses a pair of motor-driven working air fans rotating about an axis.

As shown prior art FIG. 1, such designs draw air into a housing via an aperture A at the top axial center of the housing above a first stage fan B. The first stage fan includes a plurality of blades enclosed by a disc at the bottom and a frustoconical cap. Thus channels are defined between adjoining blades and, as the fan rotates, the air is accelerated through the channels in the circumferential and radially outward direction. The air is then directed into a second stage which includes a second stage fan C. The second stage fan is generally identical to the first stage fan and includes a plurality of blades enclosed by a disc at the bottom and a frustoconical cap. Air is again accelerated through the channels defined by adjoining blades in the circumferential and radially outward direction. The housing provides an outlet located proximal the fan opposed to the aperture. As is evident from FIG. 1, such fans may employ a linear taper wherein the cross-sectional height of the fan becomes linearly smaller as a function of radial distance from the axis of rotation. This in turn results in a linear constriction in the channel volumes as a function of radial distance from the axis of rotation. This feature was provided to improve airflow properties and improve efficiency. While the linear taper of such fans have been found to improve airflow certain drawbacks persist. Specifically, assemblies of this nature tend to collect contaminates such as dust and debris in the rotating working air fans. This is particularly a concern when air drawn into the fan assembly carries a dust and water mixture such as would be seen in a wet/dry vacuum. It has been found that dust and other contaminates collect in the working air fans which, over time, leads to bearing damage and eventual fan and/or motor assembly failure. Thus, while such fans are efficient and have a small profile, the aforementioned drawbacks persist.

Therefore, there exists a need in the art for a fan assembly which minimizes dust and contaminate collection on the working air fans and therefore extends the life of the fan assembly.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a first aspect of the present invention to provide a fan insert which achieves improved efficiency.

Still another aspect of the present invention is to provide a motor-driven fan assembly, comprising a motor assembly, a bracket coupled to the motor assembly, the bracket including an outlet port, a shroud assembly which defines a first chamber and a second chamber and includes an inlet port, the shroud assembly adapted to be received on the bracket, a shaft rotated by the motor assembly, the shaft extending through the bracket and into the shroud assembly, a first fan coupled to the shaft and positioned in the first chamber, and a second fan coupled to the shaft and positioned in the second chamber, wherein the first and the second fan each include a plurality of curved blades positioned between a flat disc and a cap, each cap defining a non-linear cross section.

Yet another aspect of the present invention is attained by a fan assembly associated with a motor assembly having a rotatable shaft, the fan assembly comprising a shroud assembly which includes a first shell and a second shell having a spacing bracket disposed therebetween, the first shell including a tapered wall and the second shell having a tapered wall, the tapered wall of the first shell being curved and substantially identical to a tapered wall of the second shell, the shroud assembly adapted to receive the rotatable shaft, a first fan adapted to be coupled to the shaft and positioned adjacent to the tapered wall of the first shell, and a second fan adapted to be coupled to the shaft and positioned adjacent to the tapered wall of the second shell, wherein the first and the second fan include a plurality of curved blades disposed between a flat disc and a cap, each cap being curved to match the curvature of the adjacent tapered wall.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings, wherein:

FIG. 1 is a sectional view of a prior art fan/motor assembly;

FIG. 2 is a sectional view of a fan/motor assembly made in accordance with the concepts of the present invention;

FIG. 3 is an exploded sectional view of the fan/motor assembly made in accordance with the concepts of the present invention;

FIG. 4 is a top plan view of an exemplary rotating fan; and

FIG. 5 is a top plan view of a stationary fan.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings and more particularly to FIGS. 2 and 3, it can be seen that a motor/fan assembly made in accordance with the invention is designated generally by the numeral 10. The motor/fan assembly 10 of the present invention includes a motor sub-assembly 11 and a fan sub-assembly 12. It should be appreciated that this disclosure is generally directed towards the fan sub-assembly, and thus the motor sub-assembly 11 may be of any suitable conventional construction. In one embodiment, the motor sub-assembly 11 includes a housing 13. The motor housing 13 may carry a concentrically positioned bearing 14 which receives a shaft 15 therein. The shaft 15 supports an armature 16 and a commutator 17 thereon, as well as a number of fans as will be hereinafter discussed. The motor sub-assembly further includes a plurality of field coils 19 in a manner known in the art. As is known in the art, these motor components interact to cause shaft 15 to selectively rotate. As will be hereinafter described, shaft 15 drives the working components of the fan sub-assembly.

An end bracket 30 is provided on the end of motor sub-assembly 11 opposite the motor housing 13. End bracket 30 may be generally circular and is provided to enable fan components to be coupled to the motor sub-assembly 11. End bracket 30 includes an outer flange 32 which defines the radially outer surface thereof. Outer flange 32 may be provided with a raised shoulder 34 which projects radially from and circumferentially around outer flange 32. At least one outlet 36 is provided in end bracket 30. While the outlet of the present embodiment is axially facing, it should be appreciated that other outlet designs may be employed. For example, a plurality of radially facing ports or a single tangential horn may be employed which achieve substantially the same results for exhausting air from the fan sub-assembly.

The shaft 15, which is operatively coupled to the above mentioned motor elements, extends through and is supported by end bracket 30. Accordingly, end bracket 30 includes a support ring 38 which is formed with a generally cylindrical body 40 and a flange 42, which projects radially inward from cylindrical body 40. Flange 42 defines an axially oriented opening 44 which is sized to allow shaft 15 to extend therethrough. The cylindrical body 40 is adapted to receive a bearing 46 therein. Bearing 46 thus receives and supports shaft 15 which rotates therein. A seal 48 may be positioned between flange 42 and bearing 46 to prevent contaminates from reaching the bearing 46. In such a manner, end plate 30 supports shaft 15.

Fan sub-assembly 12, which is supported by the end bracket 30, includes a shroud assembly 52 which encloses a plurality of fans as will be hereinafter discussed. It should be appreciated that, while embodiments shown in FIGS. 2-5 employ two working air fans, more than two might be employed, and stacked in the manner disclosed below. Shroud assembly 52 includes a first shell 54 which is positioned at the axial end of fan sub-assembly 12, opposite the end bracket 30. First shell 54 includes an outer wall 56 which is substantially cylindrical and centered about the axis defined by shaft 15. Outer wall 56 terminates at a radiused edge 58 which transitions to a flat axially facing wall 60. Facing wall 60 is annular and extends radially inwardly from radiused edge 58. Facing wall 60 terminates at it's radially inner edge at an axially projecting step 62. Axial step 62 is generally cylindrical and connects to a tapered wall 64 which extends radially inward and axially outwards, away from motor sub-assembly 11. As is evident from FIG. 2, the angle of tapered wall 64 varies with radial location. In other words, the cross-section of tapered wall 64 is non-linear. In one or more embodiments tapered wall may be described geometrically as having a constant radius R. In one or more embodiments the radius R of tapered wall 64 may be about four inches. It should, however, be appreciated that the tapered wall 64 may include non-linear profiles which do not include a constant radius. For example, the taper may be described as a concave curvature. In any event, tapered wall 64 terminates on its radially inner edge at a ring 66. Ring 66 is axially facing and defines an inlet port 68. Inlet port 68 provides the opening through which working air enters fan sub-assembly 12.

Shroud assembly 52 further includes a spacing bracket 70. Spacing bracket 70 includes an outer wall 72 which is substantially cylindrical and centered about the axis defined by shaft 15. As shown in FIG. 2, outer wall 56 of first shell 54 is received over a portion of outer wall 72 and rests against a step 74. Step 74 acts as a stop, against which the rim of outer wall 56 rests. In this manner the first shell 54 is stacked atop the spacing bracket 70. Outer wall 72 terminates at a radiused edge 76 which transitions to an axially facing base wall 78. Base wall 78 is generally disc shaped and projects radially inward from outer wall 72. An opening 80 is provided at the concentric center of base wall 78. As is evident from FIG. 2, the first shell 54 and spacing bracket 70 define a first chamber 82, access to which is provided at inlet port 68 and opening 80.

Shroud assembly 52 further includes a second shell 84 which is positioned between end bracket 30 and spacing bracket 70. Second shell 84 includes an outer wall 86 which is substantially cylindrical and centered about the axis defined by shaft 15. The cylindrical outer wall 72 of spacing bracket 70 is received over a portion of outer wall 86 and rests against a step 88. Step 88 acts as a stop, against which the rim of outer wall 72 rests. Outer wall 86 terminates at a radiused edge 90 which transitions to a flat axially facing wall 92. Facing wall 92 is annular and projects radially inwardly from radiused edge 90. Facing wall 92 terminates at it's radially inner edge at an axially projecting step 94. Axial step 94 is generally cylindrical and connects to a tapered wall 96 which extends radially inward and axially outwards, away from motor sub-assembly 11. As is evident from FIG. 2, the angle of tapered wall 96 varies with radial location. In other words, the cross-section of tapered wall 96 is non-linear. In one or more embodiments tapered wall 96 may be described geometrically as having a constant radius. In one or more embodiments the radius of tapered wall 96 may be about 4 inches. It should, however, be appreciated that tapered wall 96 may include non-linear profiles which do not include a constant radius. For example, the taper may be described as a concave curvature. In any event, tapered wall 96 terminates on the radially inner edge at a ring 98. Ring 98 is axially facing and defines an inlet port 100. Thus it should be evident that second shell 84 and end bracket 30 define a second chamber 102, access to which is provided at inlet port 100 and outlet 36.

As earlier discussed, shroud assembly 52 encloses a plurality of fans. First chamber 82 encloses a first working air fan 104, hereinafter first fan 104. First fan 104 includes a base 106 in the form of a disc. Base 106 is coupled to shaft 15 and, to that end, is provided with a central bore 108 which is sized to receive shaft 15 therein. As shown in FIG. 4, a plurality of blades 110 are carried by base 106 and are disposed in a curved sunburst arrangement radiating outwardly towards outer wall 56. Each blade 110 includes a leading edge 112 which is spaced from shaft 15, thus defining a fan eye 114. Each blade 110 terminates proximate to the outer radial edge of base 106 at a trailing edge 116. When shaft 15 rotates in a clockwise direction, the blades 110 of FIG. 4 further define a leading surface 118 and a trailing surface 120, as will be discussed later in more detail. In one or more embodiments, the blades 110 may be coupled to base 106 along the bottom edge thereof by a plurality of stakes or rivets (not shown) which are received in corresponding holes along base 106. Though the bottom edge of blades 110 are flat, a top edge 128 is provided with a non-linear taper. In other words, the height of blades 110, as defined as the distance from base 106, varies nonlinearly corresponding to the radial distance from shaft 15. Each adjoining blade 110 defines a channel 129 therebetween which provides a path for airflow during fan operation. Finally, a cap 130 is provided which, along with base 106 retains the blades 110 therebetween. Cap 130 matches the profile of top edge 128 of blades 110 along the top edges 128 of blades 110. Cap 130 includes a central aperture 132 which corresponds with the leading edges 114 of blades 110. And the cap 130 has an outer peripheral edge 133 that is in close proximity to the axial step 62. Accordingly, there is minimal turbulence generated between cap 130 and an underside of the tapered wall 64. In other words, parasitic airflow that would otherwise interfere with working air flow through the fan assembly is minimized. As is evident from FIG. 2, the cap 130 and corresponding blades 110 may substantially match the cross-sectional profile of tapered wall 64 of first shell 54. Thus, in one or more embodiments the cross-section of cap 130 may be described geometrically as having a constant radius. In one or more embodiments the radius cap 130 may be about 4 inches. In other embodiments, cap 130 may include non-linear cross-sectional profiles which do not include a constant radius. For example, the cross-sectional profile may be described as a concave curvature.

First chamber 82 also encloses a stationary fan 134 which is carried by spacing bracket 70. As seen in FIG. 5, stationary fan 134 includes a plurality of blades 136 which may oriented in a sunburst arrangement radiating outwardly towards outer wall 56. A disc 138 is positioned along the top surface of blades 136 and includes a central bore 140 which allows shaft 15 to project therethrough. Blades 136 extend radially inward from the outer radial edge of disc 138 and end at the central opening 80 of spacing bracket 70.

The central opening 80 of spacing bracket 70 communicates with a second working air fan 142, hereinafter second fan 142, which is inclosed within second chamber 102. Second fan 142 may be substantially identical to first working air fan 104. Thus, second working air fan 142 includes a base 144 in the form of a disc. Base 144 is coupled to shaft 15 and, to that end, is provided with a central bore 146 which is sized to receive shaft 15 therein. As shown in FIG. 4, a plurality of blades 148 are carried by base 146 and are disposed in a curved sunburst arrangement radiating outwardly towards outer wall 56. Each blade 148 includes a leading edge 150 which is spaced from shaft 15, thus defining a fan eye 152. Each blade 110 terminates proximate to the outer radial edge of base 144 at a trailing edge 154. When shaft 15 rotates in a clockwise direction, the blades 148 further define a leading surface 156 and a trailing surface 158 as will be described later in more detail. In one or more embodiments, the blades 148 may be coupled to base 144 along the bottom edge thereof by a plurality of stakes or rivets (not shown) which are received in corresponding holes along base 144. Though the bottom edge of blades 110 are flat, a top edge 166 is provided with a non-linear taper. In other words, the height of blades 148, as defined as the distance from base 144, varies nonlinearly corresponding to the radial distance from shaft 15. Each adjoining blade defines a channel 167 therebetween which provides a path for airflow during fan operation. Finally, a cap 168 is provided which, along with base 144 retains the blades 148 therebetween. Cap 168 matches the profile of top edge 166 of blades 148 along the top edges 166 of blades 148. Cap 168 includes a central aperture 170 which corresponds with the leading edges 150 of blades 148. And the cap 168 has an outer peripheral edge 169 that is in close proximity to the axial step 94. Accordingly, there is minimal turbulence generated between cap 168 and an underside of the tapered wall 96. In other words, parasitic airflow that would otherwise interfere with working air flow through the fan assembly is minimized. As is evident from FIG. 2, the cap 168 and corresponding blades 148 may substantially match the cross-sectional profile of tapered wall 96 of second shell 84. Thus, in one or more embodiments the cross-section of cap 168 may be described geometrically as having a constant radius. In one or more embodiments the radius cap 168 may be about 4 inches. In other embodiments, cap 168 may include non-linear cross-sectional profiles which do not include a constant radius. For example, the cross-sectional profile may be described as a concave curvature.

In the present embodiment, the aforementioned fans 104 and 142 are spaced and coupled to the shaft 15 by a plurality of elements. A T-spacer 172 extends inwardly through opening 44 in support ring 38 and bears against an inner race of bearing 46. T-spacer 172 may have a generally T-shaped cross section to provide an enlarged transverse surface against which the base 144 of second fan 142 may bear. Positioned between fans 104 and 142 is a sleeve spacer 174 which is received on shaft 15. A washer 176 is positioned around shaft 15 and between sleeve spacer 174 and each working air fan. A nut 178 may be provided at the end of shaft 15 which may be tightened against a washer 180 which in turn bears against base 106 of first working air fan 104. This in turn clamps together the inner race of the bearing 46, T-spacer 172, sleeve spacer 174, washers 176, fans 104 and 142 and washer 180 so that all turn as one unit with the shaft 15 as it is driven by the motor sub-assembly 11.

In this manner, when shaft 15 rotates clockwise, air is drawn into first chamber 82 via inlet port 68. Air is drawn into eye 114 and is urged radially outward by blades 110. Once the air is ejected radially outwardly past blades 110, blades 136 of the stationary fan 134 direct the air flow radially inward toward opening 80. As is evident from FIG. 2, opening 80 directs the air flow into second chamber 102. As second fan 142 rotates, blades 148 again urge the air radially outward. Because of the pressure differential between the outside atmosphere and the second chamber 102, the air exits second chamber 102 via outlet port 36. Thus, as described above, air is drawn into inlet port 68 and out of outlet port 36 upon rotation of shaft 15.

Of particular concern in such fans is the collection of dust and other particles within the working air fans. The present invention solves this problem through the cooperation of two elements. First, the use of a multi-stage fan, i.e. one which employs two working fans and a stationary fan therebetween, produces increased airflow. This feature, in combination with the non-linear profile of fan blades 110 and 148, greatly reduces contaminates from sticking to fan blades. In particular, it has been found that in conventional multi-stage fans, dust and debris sticks to the leading surface 118 or 156 as air travels radially outward from the eye 114 or 152 of the fan. By reducing the height of the caps 130 or 168 non-linearly in the radially outward direction, the cross sectional area of channels 129 and 167 is thus reduced. The reduction in channel area of the present invention is thus reduced more quickly than in a prior art fan. This reduction of area in turn accelerates the particle. Consequently, the particles in the air are accelerated faster than a traditional fan. Because the air is accelerated faster as it travels radially outward, any particles or contaminates in the air are ejected from the fan and not given an opportunity to stick to the leading surface 118 or 156. Thus, when such a non-linear taper is employed with a multi-stage working air fan design, the incidence of fan contamination is greatly reduced. This in turn leads to increased fan and bearing life. Specifically, uneven contaminate buildup, or buildup which suddenly breaks away from the blades, can cause vibration, which degrades bearing life. By preventing contaminates from sticking to the blades, this vibration is limited and bearing life is increased.

Thus, it can be seen that the objects of the invention have been satisfied by the structure presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims. 

1. A motor-driven fan assembly, comprising: a motor assembly; a bracket coupled to said motor assembly, said bracket including an outlet port; a shroud assembly which defines at least a first chamber and a second chamber and includes an inlet port, said shroud assembly adapted to be received on said bracket; a shaft rotated by said motor assembly, said shaft extending through said bracket and into said shroud assembly; a first fan coupled to said shaft and positioned in said first chamber; and a second fan coupled to said shaft and positioned in said second chamber, wherein said first and said second fan each include a plurality of curved blades positioned between a flat disc and a cap, each said cap defining a non-linear cross section.
 2. The fan assembly according to claim 1, wherein said blades are disposed on said disc in a curved sunburst arrangement radiating radially outwardly.
 3. The fan assembly according to claim 1, wherein each said blade extends from said disc to said cap.
 4. The fan assembly according to claim 1, wherein said blades are secured to said cap and said disc.
 5. The fan assembly according to claim 1, wherein said shroud assembly further comprises: at least a first shell and a second shell having a spacing bracket therebetween, said first shell includes a tapered wall having the same cross-sectional profile as said cap of said first fan and said second shell includes a wall having the same cross-sectional profile as said cap of said second fan.
 6. The fan assembly according to claim 5 further comprising a stationary fan, said stationary fan is coupled to said spacing bracket.
 7. The fan assembly according to claim 6, wherein said stationary fan comprises a plurality of curved blades and a disc, said blades are disposed between said disc and said stationary spacing bracket.
 8. The fan assembly according to claim 1, wherein said cap of said first fan includes a first fan aperture and said cap of said second fan includes a second fan aperture and when said shaft rotates air is drawn through said first and second fan apertures and radially outward across said blades.
 9. A fan assembly associated with a motor assembly having a rotatable shaft, the fan assembly comprising: a shroud assembly which includes a first shell and a second shell having a spacing bracket disposed therebetween, said first shell including a tapered wall and said second shell having a tapered wall, said tapered wall of said first shell being curved and substantially identical to a tapered wall of said second shell, said shroud assembly adapted to receive the rotatable shaft; a first fan adapted to be coupled to the shaft and positioned adjacent to said tapered wall of said first shell; and a second fan adapted to be coupled to the shaft and positioned adjacent to said tapered wall of said second shell, wherein said first and said second fan include a plurality of curved blades disposed between a flat disc and a cap, each said cap being curved to match the curvature of said adjacent tapered wall.
 10. The fan assembly according to claim 9, wherein each said blade is disposed on said disc in a curved sunburst arrangement radiating radially outwardly.
 11. The fan assembly according to claim 10, wherein each said blade extends from said disc to said cap.
 12. The fan assembly according to claim 10, wherein said blades are secured to said cap and said disc.
 13. The fan assembly according to claim 12, further comprising: a stationary fan coupled to said spacing bracket.
 14. The fan assembly according to claim 10, wherein said stationary fan comprises a plurality of curved stationary blades and a stationary disc, said stationary blades are disposed between said stationary disc and said stationary spacing bracket.
 15. The fan assembly according to claim 10, wherein said cap of said first fan includes a first aperture and said cap of said second fan includes a second aperture and when said shaft rotates air is drawn through said first and second apertures and radially outward across said blades. 